EXOhSPEC collimator mechanical design

Adithep Kawinkij; Apirat Prasit; Christophe Buisset; Griangsak Thummasorn; Teerawat Kuha; Esther Lhospice; Hugh R. A. Jones; William E. Martin; Ronny Errmann; Piyamas Choochalerm; Guillem Anglada-Escude; David Campbell; Clark Baker; Somsawat Rattanasoon; Suparerk Aukkaravittayapun; Thirasak Panyaphirawat; Apichat Leckngam; David Mkrtichian; Saran Poshyachinda; Boonrucksar Soonthornthum

doi:10.1117/12.2529107

9 September 2019 EXOhSPEC collimator mechanical design

Adithep Kawinkij, Apirat Prasit, Christophe Buisset, Griangsak Thummasorn, Teerawat Kuha, Esther Lhospice, Hugh R. A. Jones, William E. Martin, Ronny Errmann, Piyamas Choochalerm, Guillem Anglada-Escude, David Campbell, Clark Baker, Somsawat Rattanasoon, Suparerk Aukkaravittayapun, Thirasak Panyaphirawat, Apichat Leckngam, David Mkrtichian, Saran Poshyachinda, Boonrucksar Soonthornthum

Author Affiliations +

Proceedings Volume 11116, Astronomical Optics: Design, Manufacture, and Test of Space and Ground Systems II; 111161G (2019) https://doi.org/10.1117/12.2529107
Event: SPIE Optical Engineering + Applications, 2019, San Diego, California, United States

Abstract

The Exoplanet High-Resolution Spectrograph (EXOhSPEC) is a high-resolution spectrograph for the characterisation of exoplanets with the Thai National Telescope. The folded version of this instrument comprises one triplet lens to collimate the beam incident on the grating and to focus the beam reflected by the grating onto the camera. This collimator comprises three lenses L1, L2 and L3 of diameter varying between 50 mm and 60 mm. We specified the barrel to guarantee a maximum decenter of the lenses equal to 25 μm. The maximum error in the orientation of each single lens is specified to be lower than 0.03º. The proposed concept is based on a semi-kinematic mounting which is used to restrain these lenses with 6 and 30 N of preloads on the axial and lateral directions to ensure their stability. These preloads are applied to the lenses using the elastic pushing force of silicone elastomers and spring force from ball-plungers. We present the design of the collimator and the assembly method. Our Finite Element Analyses show that the maximum surface error induced by the preloads is lower than 60 nm Peak-To-Valley on each optical surface of L1, L2, and L3. We describe our manufacturing process using NARIT’s CNC machine and its validation using our Coordinate-Measuring Machine.

Citation Download Citation

Adithep Kawinkij, Apirat Prasit, Christophe Buisset, Griangsak Thummasorn, Teerawat Kuha, Esther Lhospice, Hugh R. A. Jones, William E. Martin, Ronny Errmann, Piyamas Choochalerm, Guillem Anglada-Escude, David Campbell, Clark Baker, Somsawat Rattanasoon, Suparerk Aukkaravittayapun, Thirasak Panyaphirawat, Apichat Leckngam, David Mkrtichian, Saran Poshyachinda, and Boonrucksar Soonthornthum "EXOhSPEC collimator mechanical design", Proc. SPIE 11116, Astronomical Optics: Design, Manufacture, and Test of Space and Ground Systems II, 111161G (9 September 2019); https://doi.org/10.1117/12.2529107

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